Organic EL Luminance Stabilization via Adaptive Voltage Control
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Solution Overview
Problem
Image display devices with organic electroluminescence (EL) elements face challenges in maintaining constant light-emitting luminance due to changes in the characteristics of thin film transistors (TFT) and organic EL elements over time, as well as temperature fluctuations, leading to delayed control and luminance instability.
Innovation Solution
An image display device that includes a pixel circuit with a recognizing portion to predict parameter values based on image data, an obtaining portion to measure actual values during light emission, and a control portion to adjust the power supply voltage to maintain luminance within a reference range by comparing predicted and actual values, thereby stabilizing light-emitting luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If temperature-based control is used to adjust luminance, then luminance stability is improved initially, but the control becomes delayed and cannot adapt to characteristic changes over time
Solution Approach 1:
The patent implements a feedback mechanism by measuring the actual luminance output of the organic EL panel and comparing it with the desired luminance level. Based on this comparison, the control portion adjusts the drive signals to compensate for characteristic changes over time, enabling adaptive control that eliminates delay inherent in temperature-based approaches.
Solution Approach 2:
The system uses the panel's own actual luminance output as the basis for control adjustments. By having the panel self-report its performance through luminance measurement, the system can automatically adapt to aging and characteristic drift without external intervention or delayed temperature-based control.
2Stability of the object's composition
If continuous adjustment of power supply voltage is made, then luminance stability is improved, but power consumption increases
Solution Approach 1:
The patent dynamically adjusts the power supply voltage based on actual luminance measurements and characteristic changes. Rather than continuous adjustment, the system makes targeted adjustments only when necessary, optimizing the balance between luminance stability and power consumption by adapting the adjustment frequency and magnitude to actual panel conditions.
Data Source
AI summary
It is aimed to provide a technology capable of stabilizing light-emitting luminance of an image display device. In order to achieve the above-mentioned object, an image display device includes a pixel circuit including a light-emitting element, a recognizing portion which recognizes a predicted value of a parameter on driving of the pixel circuit based on image data, and an obtaining portion which obtains an actually-measured value of the parameter while causing the light-emitting element to emit light in accordance with the image data. This image display device further includes a comparing portion which compares the predicted value and the actually-measured value with each other, and a control portion which controls a power supply voltage applied to the pixel circuit in accordance with a comparison result of the comparing portion. The control portion increases/decreases, in response to a fact that the actually-measured value falls outside a first reference range with the predicted value being as a reference, the power supply voltage so that the actually-measured value is included in a second reference range which is within the first reference range and is narrower than the first reference range, and stops the increase/decrease of the power supply voltage in a case where a relationship in which the actually-measured value is included in the second reference range is satisfied. Note that the control portion may be provided outside the image display device.